Principles and Implementation of VoIP DTMF inband

This article from csdn ucser, http://blog.csdn.net/perfectpdl reprinted to indicate the source, thank you!

DTMF is called multi-tone dual-join, also called secondary dialing. There are three methods for VoIP to carry DTMF: inband, RFC 2833 (the latest RFC is 4733, which is referenced in IMS), and SIP info.

The inband mode transfers the buffer generated by keys to the audio RTP stream, instead of defining special RTP events similar to RFC 2833. Each key (, 5 ....) Data Buffer generation can be achieved throughAlgorithmYou can also directly record the corresponding sound to the file. Then it is packaged into RTP which is uploaded to the listener through the voice channel. Generally, the listener uses DSP to detect this signal and parse the corresponding number through spectrum analysis.